Electricity has been restored to Hartsfield-Jackson Atlanta International Airport late Sunday, hours after an outage unleashed havoc on travelers around the country, leading to hundreds of flight cancellations during one of the most hectic travel periods of the year.

The power went out at Hartsfield-Jackson—the busiest airport in the world by passenger traffic, with an average of 275,000 passengers daily—shortly after 1 p.m. Sunday, according to airport officials.